Seat belt buckles in general must meet many requirements to reliably operate under any and all conditions. One specific requirement for seat belt buckles is to function when used with seat belt pretensioners (i.e., retractor, buckle or anchor pretensioners).
Seat belt pretensioners remove seat belt slack in the event of a predetermined occurrence. When pretensioners are activated this results in a very high acceleration of the webbing and subsequently, the seat belt buckle. An example of a pretensioner is a pyrotechnically actuatable device, which fires a squib wherein a resulting force will remove a predetermined amount of slack from the seat belt webbing secured to the seat belt buckle. Accordingly, and when pretensioners are activated, the seat belt buckle is subjected to a very high acceleration.
Therefore, it is desirable to provide the seat belt buckle with a locking feature or device that is engaged during activation of the pretensioners wherein movement of the release button is limited. Additionally, it is desirable to provide a seat belt buckle with an inertia locking device to maintain a latched condition during activation of the pretensioners.